Spectrum is a precious resource. With increasing usage of spectrum, interference is of increasing concern. All radio frequency communication developed to date is subject to interference. The worst type of interference occurs with intentional jamming or overloaded spectrum usage. In addition, varying propagation conditions including propagation effects such as fading and multipath can produce substantial impairment of existing systems' ability to maintain exchange of information.
It is desirable to provide a type of modulation for radio frequency transmission that is relatively more robust at delivering information from transmitter to receiver in the presence of a large variety of interference. It is also desirable that such modulation type be robust to impairments introduced by the propagation effects of the channel. It is highly desirable to provide a communication system which will support many simultaneous users of a band of communication spectrum by distributing information within a modulation in ways that are different from all other modulations, thereby making other forms of modulations unlikely to interfere with communications utilizing this modulation.